Active restoration fosters better recovery of tropical rainforest birds than natural regeneration in degraded forest fragments

Abstract

1. Ecological restoration has emerged as a key strategy for conserving tropical forests and habitat specialists, and monitoring faunal recovery using indicator taxa like birds can help assess restoration success. Few studies have examined, however, whether active restoration (AR) achieves better recovery of bird communities than natural regeneration, or how bird recovery relates to habitat affiliations of species in the community.2. In rainforests restored over the past two decades in a fragmented landscape (Western Ghats, India), we examined whether bird species richness and community composition recovery in 23 actively restored (AR) sites were significantly better than recovery in paired naturally regenerating (NR) sites, relative to 23 undisturbed benchmark (BM) rainforests. We measured eight habitat variables and tested whether bird recovery tracked habitat recovery, whether rainforest and open-country birds showed contrasting patterns, and assessed species-level responses to restoration. 3. We recorded 92 bird species in 460 point-count surveys. Rainforest bird species richness was highest in BM, intermediate in AR and lowest in NR. Contrastingly, open-country bird species richness was least in BM, intermediate in AR and highest in NR. 4. Bird community composition varied significantly across treatment types with composition in AR in transition from NR to BM. Bird community dissimilarity between sites was positively related to dissimilarity in habitat structure and floristics, and geographical distance between sites. Variance partitioning indicated that structural and floristic dissimilarity explained 90% of the variation in community composition.5. Indicator species analysis revealed significant associations of 34 species with one or more treatment types. Species associated with BM and AR treatment types were all rainforest species, while only 38% of species associated with AR and NR treatment types were rainforest species. Synthesis and applications. We show that active restoration (AR) of degraded fragments benefits rainforest birds and reduces the infiltration of open-country birds, and highlight the importance of considering rainforest and open-country species separately. In human-modified tropical rainforest landscapes, AR of degraded | 275

Listening for change: quantifying the impact of ecological restoration on soundscapes in a tropical dry forest

“…While we found no significant difference in the cumulative number of species at a site, it is noteworthy that there is a significant difference in community composition across the sites. Our results align to a limited degree with other evidence on ecological restoration, for example, from southern India, where restoration interventions are associated with a significant turnover in species richness and composition after two decades (Hariharan & Raman 2021). However, we did not find a significant difference in the total number of species detected.…”

“…Increased tropical forest fragmentation (Taubert et al 2018) and loss in recent decades have underscored the need to protect (Cook‐Patton et al 2021) and ecologically restore forests in the human‐dominated landscapes of the tropics (Grantham et al 2020; Cook‐Patton et al 2021). Ecological restoration has the potential to provide a multitude of benefits, such as conserving biodiversity (Crouzeilles et al 2016; Brancalion et al 2019), especially specialist species with specific habitat needs (Hariharan & Raman 2021), supporting natural resources‐dependent livelihoods (Erbaugh et al 2020) and, to a limited extent, mitigating climate change (Griscom et al 2017; Cook‐Patton et al 2021).…”

Forest bird decline and community change over 19 years in long-isolated South Asian tropical rainforest fragments

“…While rainforest bird density declined over time, the density of the subset of restricted-range birds in the aggregate did not show a significant decline. This contrasts with regional declines in endemic birds of the Western Ghats reported from citizen science studies (SoIB 2020), and landscape-level declines in species such as the endemic Malabar Grey Hornbill in the Anamalai Hills (Hariharan & Raman 2022). Stability in density of range-restricted species over time may be due to range-restricted species being limited in their geographic extent but not necessarily in abundance within specific parts of their range: Half of all range-restricted birds (11 of 22), such as White-cheeked Barbet Psilopogon viridis , Black-throated Munia Lonchura kelaarti and Malabar Barbet Psilopogon malabaricus , are commonly found in human modified landscapes like coffee plantations (Karanth et al 2016), home gardens (Sidhu et al 2010) and urban wooded areas (Praveen et al 2022) within their restricted geographic ranges.…”

“…Overall, we highlight a worrying decline in populations of rainforest birds, with potentially adverse impacts on bird conservation and downstream ecosystem functions in the future. Long-term conservation of tropical birds in old forest fragments therefore requires additional efforts such as protecting forest fragments irrespective of size (Turner & Corlett 1996), improving habitat quality through active and passive restoration (Hariharan & Raman 2022), and mitigating forest loss and fragmentation (Taubert et al 2018). Maintaining ecosystem functions and stable populations of rainforest birds may further require mitigating regional stressors from global climate (Barlow et al 2018, Lees et al 2022, Ramesh et al 2022).…”

Bornean tropical forests recovering from logging at risk of regeneration failure

“…While the co‐benefits of biodiversity recovery during silvicultural approaches for biomass recovery are often presumed (Crouzeilles et al., 2017; Hariharan & Shankar Raman, 2022; Osuri et al., 2022), it remains unknown whether active restoration through these means delivers recovery of the reference community assemblage. Our study shows that 15–27 years after implementation of active restoration via rehabilitative silvicultural treatments in the logged forests, the richness and evenness of seedling communities were higher than those in adjacent NR forests and more closely resembled those of the seedling communities in UL forest, while nonetheless remaining distinct from these, in the initial 2 months after masting.…”